1. Field of the Invention
The invention relates generally to seismic exploration and, more particularly, but not by way of limitation, it relates to improved exploration methods utilizing elliptically polarized shear waves that carry a greater amount of information as contained in each of compressional and shear waves.
2. Description of the Prior Art
The present inventors are aware of no prior use of elliptically polarized shear waves in seismic exploration practice. While numerous procedures have been utilized for a number of years for both compressional wave exploration and shear wave exploration, there apparently has been no conception of the existence of an orderly elliptically polarized shear wave, circular in the specific case, which imparts particle motion in three orthogonal dimensions as it travels through an earth medium. Accordingly, it is now conceived that the particle motion of the elliptically polarized shear wave can be detected by one or more three-dimensional orthogonal detectors to carry out any of vertical seismic profiling (VSP) procedures, refraction or reflection surveys, three-dimensional seismic surveys, and related seismic sounding practices.
The closest prior teaching yet discovered is a paper S12.7 presented at the 1983 meeting for the Society for Exploration Geophysics in Las Vegas, Nev., entitled "Shear Wave Polarizations: A Plea for Three-Component Recording" by Stuart Crampin. While this paper recognized the fact that a greater of volume of knowledge may be extracted from shear wave data and that such additional data would show up through three-dimensional detection, the author was not aware of the elliptic polarization character of such shear waves and their adherence to specific propagation properties.